Street lighting system



June 5, 1934. DMD' KNOWLES Re. 19,199

STREET LIGHTING SYSTEM Original Filed Aug. 22, 1928 k Q Lg.

: INVENTOR DeweyD Know/es.

ATTORNEY UNITED STATES PATENT OFFICE STREET LIGHTING SYSTEM Dewey D.Knowles, Wilkinsburg, Pa., assignor to Westinghouse Electric &Manufacturing Company, a corporation of Pennsylvania Original No.1,788,111, dated January 6, 1931, Serial No. 301,415, August 22, 1928.Application for reissue April 11, 1931, Serial No. 529,536

12 Claims. (Cl. 25041.5)

My invention relates to control systems and high electrical resistancewhen not subjected to particularly to circuit-controlling means emanylight, such as daylight, while its resistance ploying light-sensitivecells. decreases very appreciably if subjected to light It is one of themain objects of my invention of any appreciable intensity. The cell 21is prefto provide a control system for power consumerably mounted in a.light-tight box 22 having 60 ing circuits embodying light-sensitivecells to an opening 23, therethrough, to permit daylight actuate thecontrol devices in accordance with or other light to strike the cell 21and cause it major variations from light to darkness and to change itselectrical resistance. vice versa, in which minor variations in light Anauxiliary light source is represented by a intensity shall be preventedfrom causing relamp 24 also located within the box 22 and so peatedenergization and deenergization of the connected to the contactor 13 asto be enerlighting units. gized when the coil 14 is energized and to beIn practicing my invention, I provide an elecdeenergized when thebridging member 16 is tromagnetic circuit controller for controlling thein operative engagement with the contact memenergization of one or morepower-consuming bers 17, at which time the lighting units 19 are 70devices, a light-sensitive cell for controlling an energized.electro-magnetic relay and an auxiliary lighting When a control systemof this kind is used' unit, the energization of which is controlleddifor street-lighting circuits, the cell 22 is to be rectly by theelectro-magnetic relay and secondsubjected to daylight and to darknessin order 0 arily by the light-sensitive cell. to properly control theenergization of the light- 75 In the single sheet of drawings, ing units19. It may happen, however, that the Figure 1 is a schematicillustration, partially intensity of the light may rise to such value asin section, of circuits and apparatus embodying to cause deenergizationof the units 19 by reamy invention; son of the decrease in theresistance of the cell Fig. 2 is a diagram of light intensities which 21and the flow of current therethrough and vary from darkness to daylight,and, through the coil 14 of the contactor 13. If a Fig. 3 is a diagramshowing the variation in momentary decrease in the light intensityshould light intensities when changing from daylight be so great as tocause the resistance of the cell to darkness. 21 to increase to arelatively high value, the 30 Referring more particularly to Fig. 1 ofthe lights would again be energized and this might drawing, I have thereillustrated a supply cirhappen several times, thereby causing undesiredcult comprising conductors 11 and 12, an elecoperation of the system.tro-magnetic relay or contactor 13 embodying Referring to Fig. 2 of thedrawing, I have an actuating coil 14 and a core member 15 asthereillustrated a curve 25 of increasing major 35 sociated therewith andhaving secured thereto a light variations, the intensity starting atzero, con a td member A p a y of or at some very low value, as may bethe case lower contact members 17 are engaged by the during the night,and increasing up to say 35 bridging member 16 when the coil 14 isdeenunits of intensity, which value may be sufficientergized. A pair ofupper contact members 18 ly high to cause the system to operate to de-40 are engaged by the bridging member 16 when energize the units 19.This will be the case if coil 14 is e e dthe cell 21 is so constructedand adjusted as to A plurality of lighting units d at d g ndecrease itsresistance sufliciently when the light e a y y for the P p Of st at g aintensity reaches say 30 foot candles, power-consuming circuit, may beconnected in The auxiliary light 24 will then be energized 5parallel-circuit relation, relatively to each other, simultaneously withthe deenergization of the and their energization is controlled by theconlighting units 19, and, therefore, the curve of tactor 13. However, Idesire it to be understood light intensity reaching the cell 21 will bethat that the circuit shown is illustrative only and Shown in thebroken-line curve 26. Even th any li y i branch circuit r c nthough thelight intensity should be momenta- 50 trolled Circuit may beSubstitutedrily reduced by 10 foot candles, the minimum Means forcontrolling the actuation of the conintensity of light reaching the cell21 will still tactor 13 comprisesalight-sensitive cell 21 which be 35units, which value is sufiiciently high to is shown generally only, andmay, for example, maintain the contactor in its operated position. be aselenium cell. It is well known that se- Several minor variations areindicated by curves lenium has the property of having a relatively 25and 26, the minimum values in no case falling below that necessary tomaintain the energization of the coil 14.

Referring to Fig. 3 of the drawing, I have there illustrated a curve ofdecreasing major intensity of light, such as may occur at nightfall. Thebroken-line curve 28 illustrates the intensity of the light reaching thecell 21, inasmuch as the auxiliary lamp 24 is still energized. Once thelight intensity, as represented by curve 28, reaches a value of 28 footcandles, the resistance becomes high enough to sufficiently decrease thecurrent traversing it and the coil 14 to permit deenergization of thecoil 14 and consequent energization of the units 19.

As soon as the total light intensity reaching the cell 21 drops to avalue of 28 foot candles, as indicated by the numeral 29, the auxiliarylight source is extinguished, and the amount of light reaching the cellwill be that shown in curve 27 to the right of the vertical lineextending below the point 29.

It is, of course, obvious that the amount of illumination provided bythe auxiliary light 24 may be varied within relatively wide limits, butI have drawn curves 25 and 26 and 2'7 and 28 with a difference of 10units of light intensity therebetween. Provided that the variations ofthe light intensity on the outside of the box 22 do not exceed 10 lightunits, the system will operate as described above and, in case actualtests show that greater variations in light intensity will occur atdaybreak or at nightfall, it is only necessary to provide a largeramount of auxiliary illumination.

The device and system embodying my invention thus provide a relativelysimple and easily operated control system which is effective to preventrepeated energization and deenergization of any controlled circuit suchas the lighting units shown incident to minor variations in the lightintensity.

While, for purposes of illustration only, I have shown and described myinvention as applied to a lighting circuit, I do not desire to belimited thereto, as it may obviously be used to control any work circuitor secondary control circult. For instance, the circuit described mightbe employed to start up a generator in an automatic substation on theapproach of darkness.

Various modifications may be made in the device and system embodying myinvention without departing from the spirit and scope thereof, and Idesire, therefore, that only such limitations shall be placed thereon asare imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

1. In a control system, in combination, an energy-translating device tobe controlled, a circuit controller therefor, a light-sensitive cell forcontrolling the energization of the circuit controller, a light sourceoperatively associated with the cell, and means associated with thecontroller for energizing the light source when the energytranslatingdevice is deenergized.

2. In a control system, the combination with a controlled circuit, acircuit controller therefor, and a light-sensitive cell for controllingthe energization of the circuit controller, of a lamp operativelyassociated with the cell and means for causing energization of the lampwhen the first named control circuit is deenergized.

3. In a control system, the combination with a controlled system, andmeans, including a light-sensitive cell subjected to varying lightintensity, for controlling the energiration of the controlled system, ofmeans operatively associated with the cell for locally increasing theintensity of light to which the cell is subjected when the variablelight intensity has increased to a predetermined value.

4. In a control system, the combination with a system to be controlled,and means, including a light-sensitive cell subjected to majorvariations of light intensity, for controlling the energization of thecontrolled system, of an auxiliary source of light operativelyassociated with the cell, and means for controlling the auxiliary lightsource to counteract the effect of minor variations of light intensityon the cell.

5. In a control system, the combination with a system to be controlled,and means, including a light-sensitive cell subjected to varying lightintensity, for controlling the energization of the controlled system, ofmeans operatively associated with the cell for locally decreasing theintensity of light to which the cell is subjected when the variablelight intensity has decreased to a predetermined value.

6. In a control system, the combination with a system to be controlled,a circuit controller therefor and a light-sensitive cell subjected to aslow major increase of light intensity for controlling the operation ofthe circuit controller, of an auxiliary source of light operativelyassociated with the cell, and means associated with the circuitcontrolled for suddenly increasing the local light intensity to whichthe cell is subjected when the light intensity has reached apredetermined value by reason of the slow major increase.

7. In a control system, in combination, an energy-translating device tobe controlled, a circuit controller therefor, a photo-sensitive device,subject to varying light intensity, for controlling the energization ofsaid circuit controller, and regulating means operatively associatedwith said photo-sensitive device and responsive to the condition of saidcontroller to abruptly increase the state of excitation of saidphoto-sensitive device when said translating device has been renderedinactive and to abruptly decrease the state of excitation of saidphoto-sensitive device when said translating device has been renderedactive.

8. In a control system, in combination, an energy-translating device tobe controlled, a current-responsive circuit controller therefor, aphoto-sensitive device, subject to varying light intensity, forcontrolling the energization of said circuit controller, and regulatingmeans operatively associated with said photo-sensitive device andresponsive to the condition of said controller to abruptly increase thecurrent exciting said controller when said translating device has beenrendered inactive and to abruptly decrease the current exciting saidcontroller when said translating device has been rendered active.

9. In a control system, in combination, an energy-translating device tobe controlled, a circuit controller therefor, a photo-sensitive device,subject to varying light intensity, for controlling the energization ofsaid circuit controller, and regulating means operatively associatedwith said photo-sensitive device and responsive to the condition of saidcontroller to abruptly increase the state of energization of saidcontroller when said translating device has been rendered inactive andto abruptly decrease the state of energization of said controller whensaid translating device has been rendered active.

10. Apparatus of the character described comprising a relay, acontroller for energizing the relay, a circuit closed by the relay, asource of energy in said circuit, and a feed-back connection betweensaid circuit and said controller whereby said source causes saidcontroller to supply more energy to said relay the moment it is closed.

11. In a controlling system, in combination, a circuit to be controlled,a current responsive controller therefor, means responsive to a variablephysical condition for actuating the controller from one circuitcontrolling position to a second circuit controlling position, meanseffective upon completion of movement of said controller from said oneposition to the second position for increasing the total value of thecondition imposed on said condition responsive means, said lastmentionedmeans being effective to decrease the total value of the conditionimposed on the condition responsive means after the controller has beenmoved from the second position to said one position, whereby relativelysmall changes in the value of the physical condition imposed on thecondition responsive means are ineffective to actuate the controller.

12. In a controlling system, in combination, a circuit to be controlled,a current responsive controller therefor movable to a first and to asecond circuit controlling position, means responsive to a variablephysical condition for controlling the energization of said controllerand for effecting movement thereof from said first to said secondposition and from said second to said first position, and meansresponsive to the position of said controller and operative when thecontroller is in said first position to modify the energization thereofin the same sense as the variation in energization causing operation ofthe controller to said first position and operative when the controlleris in said second position to modify the energization thereof in thesame sense as the variation in energization causing operation of thecontroller to said second position, so as to maintain the controlledcircuit in the condition to which it has been last actuated by thecontroller to avoid a reverse operation upon a minor variation in saidphysical condition in the opposite sense.

DEWEY D. KNOWLES.

